FRESNO, Calif. (AP) — A Central California mother and her four children were killed in fiery crash during the weekend after a vehicle ran a stop sign and hit their SUV.

The crash occurred after 7 p.m. Saturday when a 2004 Nissan Quest minivan ran a stop sign and hit the 29-year-old woman and her four children — boys ages 1 and 3 and girls ages 6 and 11 — riding in a 2003 Ford Expedition SUV at an intersection in Fresno County, California Highway Patrol Officer Axel Reyes said. Within minutes, the SUV was engulfed in flames.

The woman’s husband, driving a quarter mile behind the SUV, saw the vehicle burst into flames and tried unsuccessfully to free his family from the vehicle, including breaking the windows, Reyes said. He received minor burns to his hands. His wife and four children died at the scene.

The minivan’s driver, 41-year-old Juana Martinez Bejarano, was hospitalized for major injuries. CHP officers and fire officials are investigating the crash and the fire.

Coroner’s investigators haven’t confirmed the identities of the burned bodies.

A witness said the minivan was traveling about 60 mph or near the 55 mph limit of county roads in the area, Reyes said.

Speed is not considered a factor in the crash; neither are drugs and alcohol, he said.

“You almost could not have timed it any better, the two front corners” of the two vehicles struck at the worst angle– right near the engine blocks — likely leading to the fire, Reyes said.

Investigators are also looking at whether Bejarano was on medication at the time of the accident, Reyes said. Her medical history indicates that may be a possibility, he said.

Fresno County Coroner Dr. David Hadden said investigators were conducting autopsies Sunday morning. The couple had been headed to pick up another child, which is why they were in two cars, Hadden said. It’s unclear whether the child was their own or a relative.

The crash was a tragedy for the Fresno County community, where it’s impossible to not routinely bump into people one knows, Hadden said. Everyone involved in the accident was from the small town of Riverdale in Fresno County, which is just north of where the crash occurred. The town is about 80 miles south of Merced.

Distraught family members gathered along with the father at the crash site Saturday evening, Reyes said.

Otto Warmbier was arrested in January 2016 at the end of a brief tourist visit to North Korea. He had been medically evacuated and was being treated at the University of Cincinnati Medical Center when he died at age 22.